Oil from the eucalyptus tree (Eucalyptus globulus) is used today in many over-the-counter cough and cold products, to relieve congestion. Eucalyptus oil is also found in creams and ointments used to relieve muscle and joint pain, and in some mouthwashes.

The eucalyptus tree is native to Australia and serves as the main food for koalas. The oil was used in traditional Aboriginal medicines to heal wounds and fungal infections. Teas made of eucalyptus leaves were also used to reduce fevers. Eucalyptus soon spread to other traditional medicine systems, including Chinese, Indian (Ayurvedic), and Greek and European.

In 19th-century England, eucalyptus oil was used in hospitals to clean urinary catheters. Laboratory studies later showed that eucalyptus oil contains substances that kill bacteria. It also may kill some viruses and fungi. Studies in animals and test tubes also found that eucalyptus oil acts as an expectorant, meaning it loosens phlegm.

There are many species of eucalyptus. Some are the size of an ornamental shrub, and some grow to be giant trees. The type of eucalyptus that is most often used as medicine is called blue gum or Australian fever tree. It can grow as high as 230 feet. Its 4 - 12 inch leaves are dark green and shiny. Its blue-gray bark peels to reveal a cream-colored inner bark.

Although eucalyptus oil has been used orally to treat some conditions, the oil is toxic when taken by mouth and must be diluted. You should not take eucalyptus oil by mouth unless your doctor tells you to.

Cough and cold

Eucalyptus is used in many medicines to treat coughs and the common cold. It can be found in many lozenges, cough syrups, rubs, and vapor baths throughout the United States and Europe. Herbalists often recommend using fresh leaves in teas and gargles to soothe sore throats and treat bronchitis and sinusitis.

Ointments containing eucalyptus are also applied to the nose and chest to relieve congestion. Eucalyptus oil helps loosen phlegm, so many people inhale eucalyptus steam to help treat bronchitis, coughs, and the flu.

Plaque and gum disease

Eucalyptus oil is also rich in cineole, an antiseptic that kills bacteria that can cause bad breath. Eucalyptus is used in some antiseptic mouthwashes, along with other oils, and the mouthwashes have been shown to help prevent plaque and gingivitis.

Other uses

On the skin, eucalyptus oil has been used to treat arthritis, boils, sores and wounds. The oil is also used in some insect repellents, and one study found that an oil of lemon eucalyptus product may also keep ticks away.

The leaves and oil of the eucalyptus plant are used as medicine. Eucalyptus oil consists of the volatile oil made from the fresh leaves and branch tops of the eucalyptus plant. Eucalyptus leaves contain tannins, which are believed to help reduce inflammation; flavonoids, plant-based antioxidants; and volatile oils.

Eucalyptus oil is available in many products, including liquids and ointments. The leaves of the eucalyptus plant are available fresh, dried (to be used in teas), and in liquid extracts. Commercial cough drops, syrups, vaporizer fluids, liniments, toothpastes, and mouthwashes may contain eucalyptus oil or its active ingredient, cineole. Some of the familiar over-the-counter remedies that contain eucalyptus oil include Listerine, Mentholatum Cherry Chest Rub, and Vicks VapoRub.

Do not give a child eucalyptus orally (by mouth), as it is toxic. Do not give cough drops containing eucalyptus to children under 6.

For a cold, don’t apply eucalyptus oil, salve or chest rub to the face or nose of a child under 2. Ask your doctor before using eucalyptus oil as a chest rub for your child or to inhale steam for congestion.

Adult

Do not take eucalyptus oil orally (by mouth) except under your doctor’s supervision, as it is toxic.

The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, contain components that can trigger side effects and that can interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a health care provider qualified in the field of botanical medicine.

Eucalyptus oil is generally safe when applied to the skin of adults. Don’t apply eucalyptus oil, salve or chest rub to the face or nose of a child under 2.

People with asthma, seizure disorders, liver or kidney disease, and low blood pressure should not use eucalyptus without first talking to their doctors.

Pregnant and breastfeeding women should not use eucalyptus.

Eucalyptus oil is toxic when taken by mouth. Do not take eucalyptus oil except under your doctor’s supervision.